They used stem cells plucked from the thin ring around the iris to make a clear cornea that allowed vision for at least 10 years.

Usually the cornea repairs itself using these cells from the limbus. But in some burn patients, the limbus is destroyed and the cornea instead develops from cells that cover the white of the eyeball, known as the bulbar conjunctiva.

When that happens, the cornea is not transparent.

In those cases, a conventional cornea transplant only provides temporary relief because the cells that caused clouding in the first place eventually take over.

The team from the Center for Regenerative Medicine Stefano Ferrari in Modena, Italy, has been extracting stem cells from the limbus of the patient's healthy eye, growing them into a thin sheet and, ultimately, grafting it to the eye to created a clear regenerating cornea.

Only one square millimeter of limbus tissue is required.

The findings, reported in the New England Journal of Medicine, show that "at least one kind of therapy can give stable results for up to 10 years," Graziella Pellegrini, who worked on the study, said in a telephone interview.

Stem cells are the body's master cells, giving rise to a variety of tissue types. In this case the researchers used so-called adult stem cells, which are partly developed cells found throughout the body.

The treatment was successful in nearly 77 percent of the 112 volunteers, allowing them to see well again, although some needed more than one graft.

Nearly all patients had lost vision from heat or chemical burns. One 80-year-old man had suffered severe eye damage 72 years earlier.

Even when not completely effective, the treatment usually alleviated a patient's sensitivity to light and eye pain, Pellegrini said in a telephone interview. "In any case, the patient has improvement in symptoms," she said.

The researchers were also able to pinpoint which types of cells were more likely to work well.

The technique was first performed in 1995. Pellegrini said it has now been done on 252 patients.